Mun Chun Kwak is fighting the 90-hour workweek.

He wants to put in longer hours.

Mr. Kwak and his wife, Hi Ja Kwak, sell liquor and sundries from behind a bulletproof partition at their corner store at Biddle and Chester streets in East Baltimore. Between them, the Korean-American couple cover a 137-hour week.

Now city officials want the Kwaks and about 150 other liquor store owners -- mainly Koreans operating in poor, mostly black neighborhoods -- to close on Sundays and cut back their hours on other days to 9 a.m. to midnight.

The Kwaks don't like it.

"I can only survive working long hours," said Mr. Kwak, 56, who was an economist in his native South Korea. "They're supposed to encourage us, not to destroy our business."

The issue is that stores like the Kwaks' Biddle Liquor are licensed as taverns but operate like package goods outlets. The only signs of tavern life at Mr. Kwak's store are a few stools in the back. Any drinks are passed through the Plexiglas partition.

The Citywide Liquor Coalition, an alliance of 35 community groups, has been trying for two years to close "taverns" like the Kwaks' on Sundays and cut back their hours. The groups say the liquor outlets attract loiterers who drink on the street, urinate in the alleys, and intimidate schoolchildren early in the morning and churchgoers on Sundays.

"We don't need seven-day package goods stores," said the Rev. Norman A. Handy Sr., co-chairman of the coalition. "Liquor stores are the site of the most loitering and the most unacceptable behavior in our communities.

"The difference between a neighborhood and a ghetto is a neighborhood has say-so. Enough is enough. We refuse to be a ghetto," Dr. Handy said.

A block away from Biddle Liquor is Joey's Cut Rate, a liquor store virtually identical to the Kwaks' business except for two details: it doesn't have the stools and it doesn't have a Class BD-7 tavern license.

As a result, while Biddle Liquor is open Sundays, Joey's Cut Rate is closed. That's because it's a package goods store, and they aren't allowed to open Sundays. Owner Joseph Chapman doesn't think that's fair.

"If he can open up seven days, then I should be able to," said Mr. Chapman, who has owned Joey's Cut Rate for 17 years. "Sunday's the best day for him because all the regular package goods stores are closed."

Although relations between Korean merchants and black city residents sometimes have been tense, people on both sides say race and ethnicity are not at the heart of this dispute.

"I don't have any animosity against him," Mr. Chapman, who is black, said of Mr. Kwak. "If I were a white guy, I would feel the same way. Why can he open Sundays and I can't?"

Dr. Handy said the coalition was "not raising the issue based on the ethnicity of the owner. To us this is not a matter of who the proprietor is, but what the proprietor does."

In the past, a legal loophole has kept the city liquor board from closing stores like the Kwaks' on Sundays. But now officials have launched a three-pronged offensive:

* The city's state senators are backing a bill (SB346) that would close the loophole and authorize the city liquor board to issue a new type of license to about 150 BD-7 license holders who don't operate full-fledged taverns. The new Class A-2 package goods license would ban Sunday sales and restrict hours other days. A hearing on the bill is scheduled today.

* The liquor board plans to issue regulations restricting BD-7 licenses to outlets where the bar operation occupies more space than package goods.

* The City Council will be asked to let store owners who accept the new A-2 license operate in residential areas. Those who continue their old operations without the A-2 license run the risk of being closed by zoning officials.

When all the pieces are in place, the BD-7 license holders will be forced to make a choice by May 1993: Either take down the bulletproof partitions and operate as a tavern or accept the A-2 package-goods license that bans Sunday sales and reduces weekday hours.

"The spirit behind this whole effort is to accommodate the business owners and also to allow for the community's input," said David C. Tanner, the city zoning administrator.

But Andrew Lee, a spokesman for the Korean Liquor Store Association, argues that the city is changing the rules in the middle of the game and says shorter store hours would cost the state sales tax and lottery revenues.

He favors a compromise -- open the stores at 9 a.m. weekdays, after children have gone to school, and at 1 p.m. Sundays, after church is out. But he acknowledges such a compromise is unlikely.

"Our side is weak, they are strong," he said.

Like other store owners, Bong Il Joo says he can't take down the bulletproof partition in his liquor outlet at North Caroline and East Preston streets.

Mr. Joo pointed to a bullet hole in the wall, next to which he had scrawled "3/11/87." That was the day a 9mm round shattered his store's plate glass window (since replaced with brick), ripped through the wire mesh above the Plexiglas partition and lodged in the wall.

"Years ago, I ran a small grocery with no bulletproof glass. I was the victim of four or five robberies. I'm lucky I'm still alive," Mr. Joo said.

Mr. Joo still runs a small tavern operation behind the bulletproof partition. A security buzzer opens the door to a little space with three stools and two video poker machines. A cluster of neighborhood regulars, who call the Korean owner "Joe," gather there every afternoon. Only regulars are admitted.

"I'd like to see it stay just the way it is," said Melvin Tucker, 66, a retired construction worker. "This bar has never been closed up, nary a day for 40 years. I'm getting old now. I have to go somewhere to drink me some beer."

If the bulletproof partition came down, Mr. Tucker said, "I wouldn't come in here."

For all the camaraderie on Caroline Street, Dr. Handy said the liquor outlets actually tear apart neighborhoods much more than they bind them together.

"Businesses have the right to recoup their investment, but not to the detriment and harm of the environment in which they operate," he said.

"This is a compromise. If you don't want to be a tavern because of safety concerns, you can convert to Class A-2 and keep up your Plexiglas," he said. "If that means you cut down your profit a little, so be it."